Conventionally, a turbomachine comprises at least one shaft connected to at least one turbine wheel (which turbine wheel may be free or linked) the shaft being arranged horizontally, i.e. with its axis oriented in a direction that is substantially perpendicular to the direction of gravity. In order to hold the shaft appropriately and support its weight, a plurality of bearings are distributed along the shaft, generally two bearings. Thus, in a turbomachine comprising in succession from upstream to downstream: a compressor, a combustion chamber, and a turbine, one bearing is located upstream from the compressor, and another bearing is located downstream from the combustion chamber. That presents several drawbacks.
A first drawback is that the shafts are often long and heavy, and in spite of the point support provided by each bearing, there remain long portions that are cantilevered out and in which the shaft can deform as a result of its own weight and of the weight of the turbine wheel(s) it carries. Such static deformation modifies the straightness of the shaft, and creates an unbalance while the turbomachine is in operation and the shaft is revolving about its own axis.
A second drawback is associated with the presence of a plurality of bearings, thereby increasing the weight of the turbomachine and decreasing its efficiency.
Finally, a third drawback is that the bearing that is located downstream from the combustion chamber is in a zone of the turbomachine that is particularly hot, where it is subjected to high levels of thermal stress. In order to ensure that that bearing operates properly, and in order to avoid any risk of it coking, it is necessary to provide a cooling system, conventionally using a cooling oil circuit. Such a cooling system is complex to install and to maintain, and it increases the costs of manufacturing and maintaining the turbomachine, as well as further increasing its weight.